Excess Deaths Associated with Rheumatic Heart Disease, Australia, 2013–2017

During 2013–2017, the mortality rate ratio for rheumatic heart disease among Indigenous versus non-Indigenous persons in Australia was 15.9, reflecting health inequity. Using excess mortality methods, we found that deaths associated with rheumatic heart disease among Indigenous Australians were probably substantially undercounted, affecting accuracy of calculations based solely on Australian Bureau of Statistics data.

We calculated observed and background mortality rates (both crude and age-specific per 100,000 person-years).We calculated age-standardized mortality rates by using the direct method, standardized to World Health Organization World Standard Population 5-year age groupings for 2000-2025.For observed mortality rates (Figure 1), RHD diagnoses from January 1, 2013, through December 31, 2017, contributed person-time from whichever time was latest (denominators): first diagnosis date or January 1, 2013.Deaths during 2013-2017 contributed to observed mortality rate numerators.For background mortality rates (Figure 1), we used age group-specific deaths of Indigenous and non-Indigenous Australians (numerators) and residential population denominators from the ABS (13).
We calculated excess mortality rates as the difference between the observed and background mortality rates (within matched age/population stratum; Figure 1).We derived 95% CIs by using nonparametric bootstrap methods, assuming a Poisson distribution (Appendix).We calculated expected RHD-related deaths by applying excess mortality rates to person-years within the RHD study cohort age/population stratum (Appendix Table 2).We calculated observed and excess mortality rate ratios (MRRs) with 95% CIs by comparing Indigenous with non-Indigenous populations with RHD.
In 2013-2017 in Australia, the background mortality rate was 193.6 deaths/100,000 Indigenous person-years and 72.3 deaths/100,000 non-Indigenous  ).Background age-specific mortality rates increased with advancing age in both populations but were always 2-to 3-fold higher for the Indigenous than non-Indigenous population (Table , Figure 2).
For the RHD study cohort, we estimated excess mortality rates of 1,166 deaths/100,000 Indigenous person-years and 771 deaths/100,000 non-Indigenous person-years, generating an MRR of 1.5 (Table ).Excess mortality rates were highest among Indigenous persons 45-64 years of age for whom the peak excess MRR of 2.1 was observed (Table ; Figure 2).Excess mortality rates applied to RHD study cohort strata estimated that 319 Indigenous and 272 non-Indigenous deaths were directly or indirectly associated with RHD (Table ; Appendix Table 4).By comparison,  ABS RHD-coded deaths captured 145 Indigenous deaths, less than half the expected cases (174 fewer than expected), but 300 non-Indigenous deaths, approximately the same as expected (28 more).
Accuracy of our estimates is limited by the quality of the coded information within source datasets and constrained by available data, including nonavailability of migrant population denominator information for rate calculations.The RHD mortality rates that we report also do not capture the profound effects that those deaths had on families, communities, and cultures.

Conclusions
After adjusting for background mortality in Indigenous and non-Indigenous populations, we found that excess deaths were higher among persons with RHD.The excess mortality method applied to the RHD study cohort estimates both direct and indirect RHD-associated deaths and reduces concerns regarding misclassified and missing cause of death arising from use of ABS RHD-coded data only.Our method is particularly useful with the Indigenous population, for whom missing ABS RHD-coded data are an issue.RHD is probably not the only underlying driver of observed excess premature deaths; rather, RHD is a potent marker of the inequities experienced by Indigenous Australians and drives excess deaths indirectly in synergy with other chronic health conditions associated with social determinants.Expected deaths among non-Indigenous persons corresponded closely to ABS RHD-coded records; however, among the Indigenous population, excess deaths were more than twice those recorded in ABS (2).Similar to other chronic illnesses (diabetes and dementia [10,14]), the burden of RHD-associated deaths in Australia is potentially underascertained when based exclusively on ABS RHD-coded records, especially among Indigenous persons, for whom cause-of-death data are missing for >10% and multiple comorbidities, along with underlying RHD, contribute to death (2).Before Australia can achieve its RHD elimination goals, improved quality of Indigenous cause-of-death data and identification of synergistic factors contributing to excess RHD-associated deaths are needed (7).
Coroners, and the National Coronial Information System and the Victorian Department of Justice for enabling Cause of Death Unit Record File data to be used for this project.Furthermore, we thank the data custodians and data managers for providing inpatient hospital and emergency department data (5 states and territories), RHD registers (5 states and territories), the Australian and New Zealand Society of Cardiac and Thoracic Surgeons Cardiac Surgery Database (single registry covering 5 states and territories), the Royal Melbourne Children's Hospital Paediatric Cardiac Surgery database (single data source for RHD pediatric patients from South Australia and Northern Territory receiving surgical intervention in Melbourne), and the Northern Territory Department of Health primary healthcare data.During outbreaks of influenza, coronaviruses, and other respiratory diseases, telework is a tool to promote social distancing and prevent the spread of disease.As more people telework than ever before, employers are considering the ramifications of remote work on employees' use of sick days, paid leave, and attendance.
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Figure 1 .
Figure 1.Data sources, cohort selection, and calculations generated in study of excess deaths associated with rheumatic heart disease, Australia, 2013-2017 (2,9,10).The main study outputs are observed mortality rates, excess mortality rates, and expected RHDassociated deaths (bottom row).ABS, Australian Bureau of Statistics; RHD, rheumatic heart disease.

Figure 2 .
Figure 2. Excess RHD-associated mortality by Indigenous status and age at death, Australia, 2013-2017.A) Indigenous; B) non-Indigenous.Background mortality rates (from the Australian Bureau of Statistics) were subtracted from the observed mortality rates (in the RHD study cohort), generating excess mortality rates (the direct and indirect RHD-associated mortality rate).RHD, rheumatic heart disease.
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Table .
Mortality rates associated with RHD among persons <65 years of age, Australia, 2103-2017* Whole population.Previously published data, reproduced with permission (2).Population-level mortality rates based on ABS RHD-coded data (RHD as an underlying or associated cause of death).
*Rates are deaths/100,000 person-years; intervals for excess mortality rates were obtained from bootstrapping of estimates (interpreted as 95% CIs).ABS, Australian Bureau of Statistics; ASMR, age-standardized mortality rate; NC, not calculated (numbers too low for reliable estimate); RHD, rheumatic heart disease.†Populationlevel, n = 14,372,851.‡Deaths from all causes within the RHD study cohort (n = 9,342).§Observed mortality rates minus background mortality rates.¶Expected number of deaths associated with RHD were calculated on the basis of excess mortality rate applied to person-years within appropriate age/population strata.# The Human Research Ethics Committees of the Health Departments of participating Australian jurisdictions provided approval for the ERASE project, which is registered on the Australian New Zealand Clinical Trials Registry (ACTRN12620000981921).Aboriginal Ethics Committee approval was sought in jurisdictions where operational and support letters were received from peak bodies of the Aboriginal Community Controlled Health Services.